1. Field of the Invention
This invention relates to the conversion of milled cereal products to soluble dietary fiber compositions which are useful in a variety of foods as sources of soluble dietary fiber.
Dietary fiber is considered to be the soluble and insoluble components of food that are not digested by enzymes in the human gastrointestinal tract. The primary sources of dietary fiber include such cell wall materials as cellulose, hemicelluloses, lignin, and pectins, along with gums and mucilages. Dietary fiber has been considered an important food component since early times. Recently, Burkitt et al. [Lancet 2: 1408-1411 (1972)] concluded that dietary fiber has a role in the prevention of certain large-intestine diseases, including cancer of the colon and diverticulitis. Diets containing large amounts of dietary fiber lead to stools that are softer and larger, and bowel movements are generally more frequent. Burkitt also mentioned that the serum cholesterol rises when dietary fiber is removed from the diet, and that eating a fiber-rich diet lowers serum cholesterol. Trowell [Am. J. Clin. Nutr. 25: 464-465 (1972) reached a similar conclusion regarding the relationship between fiber and health benefits.
It is now known that not all dietary fiber is the same and that different fibers provide different health benefits. For example, wheat bran is very rich in insoluble dietary fiber (mainly cellulose and hemicelluloses) and is excellent for decreasing the transit time of food through the digestive tract [Anderson et al., Am. J. Clin. Nutr. 32: 346-363 (1979)]. Some fiber are reported to reduce total plasma cholesterol [Munoz et al., Am. J. Clin. Nutr. 32: 580-592 (1979)].
2. Description of the Prior Art
In recent years, considerable attention has been given to oats as a source of dietary fiber. It is the soluble fiber component that is effective in lowering serum cholesterol levels. Oatmeal, or rolled oats, and especially oat bran are the best sources of this soluble fiber. The first indication of serum cholesterol lowering by rolled oats was observed in rats by Degroot et al. [Lancet 2: 303-304 (1963)]. Fisher et al. [Pro. Soc. Exp. Biol. Med. 126: 108-111 (1967)] report that the fiber fraction of oats is responsible for its unique effects on cholesterol. Over the years, numerous experiments with animals have shown that oat fiber has a strong hypocholesterolemic effect. Anderson et al. [Am. J. Clin. Nutr. 34: 824-829 (1981); 40: 1146-1155 (1984)] have confirmed hypocholesterolemic effects of oats in humans. Oat fiber also reduces the amount of low-density lipoprotein (LDL) without lowering the beneficial high-density lipoprotein (HDL). In fact, Anderson et al. [66th Annual Meeting, Am. Assoc. Cer. Chem., Abstr. No. 112 (1981)] teach that oat bran fed to humans can reduce LDL 58% while increasing HDL 82%. Other water-soluble fibers, such as pectin and guar gum, can lower serum cholesterol, but they are frequently accompanied by undesirable side effects such as nausea and vomiting. The results of another study by Anderson et al. (supra 1984) indicate that oat bran diets decrease total serum cholesterol 19% and LDL 23% and that oat bran increases bile acid excretion 65%. These studies clearly document the hypocholesterolemic effects in humans of oat products which are rich in soluble fiber.
Maltodextrins are successful commercial products prepared by hydrolysis of pure starch. The wet milling of corn is the primary source of starches from which maltodextrins are obtained. Other sources of starch for commercial products are tapioca, potato, and rice. Cereal flours are generally not used for maltodextrin production because of the flavors and colors that develop during processing [Katz, Cer. Foods World, 31: 866-867 (1986)]. Also, when cereal flours are treated with amylases, a colloidal hydrolysate is obtained that is nonfilterable (U.S. Pat. No. 4,894,242). However, some breakfast and related food products have been produced in which the characteristic cereal flavor is desired. Whole cereal flours have been subjected to starch-hydrolyzing conditions and have yielded, for example, a whole-grain hydrolyzed product [Conrad, U.S. Pat. No. 4,377,602] and a ready-to-eat, enzyme-saccharified cereal [Fulger et al., U.S. Pat. No. 4,710,286]. Ronai [U.S. Pat. No. 3,640,729] arrives at a similar product by adding prehydrolyzed starch to oat flour to yield an instant oat cereal product.